This invention relates to an improved cuvette rotor assembly used in centrifugal chemistry analyzers for the determination of a variety of serum constituents in the clinical laboratory. In particular, the invention relates to a cuvette rotor assembly having a significantly improved dam which prevents premature mixing of chemical reagents with a patient's serum or other biological fluid.
Conventional cuvette rotor assemblies such as those described in U.S. Pat. Nos. 4,123,173, 4,226,531, 4,314,970, and 4,373,812 generally comprise a disc-shaped body having about 20 space-apart recesses extending radially throughout its periphery in a circumferentially structured array. Each of the radially extending recesses (cuvettes) has fluid-filling ports or a slot in the top wall into which a patient's sample and chemical reagent are dispensed. A generally wedge-shaped barrier structure (dam) is disposed in said recess intermediate the fluid-filling passages such that the two fluids dispensed on each side of the barrier structure are kept separate from one another when the cuvette rotor is at rest.
After loading of the cuvettes is completed, the assembly is placed in a centrifugal analyzer and spun at a rotational speed of about 4,000 revolutions per minute for a period of time sufficient to effect transfer of fluid over the barrier structure and cause mixing of patient's sample with the chemical reagent. The rotational speed is then generally reduced to about 1,000 revolutions per minute and photometric measurements are made to determine the level of chemical constituent in the patient's sample. The operation of the centrifugal analyzer, the loading of the fluids in the cuvettes, and the overall construction of cuvette rotor assemblies similar to that described herein are generally well-known and do not constitute part of the present invention.
Premature mixing of a patient's sample with chemical reagents has been observed with various degrees in the cuvette rotors described hereinabove and those presently used in the clinical laboratory. Various modifications have been made to these cuvette rotors to reduce this premature mixing; however, none of these attempts have been effective in preventing this mixing. One such attempt is described in U.S. Pat. No. 4,373,812 and comprises a cuvette assembly having capillary flow inhibiting structures along the intersections between the compartment sidewalls and bottom surface, and along the substantially vertical wall portion of the dam. These capillary flow inhibiting structures, smoothly curved surface portions having a radius of curvature greater than 0.75 millimeters, are intended to retard spontaneous "creep" flow of fluid in either direction over the dam as the fluids are dispensed into the cuvette rotor at rest. Although this cuvette design somewhat retards premature mixing, it does not effectively eliminate the premature mixing and the possible cause of undesirable deviations in clinical assay values encountered with this type of cuvette rotor.
In accordance with the present invention, an improved cuvette rotor is described having a barrier structure (dam) capable of significantly retarding the premature mixing of chemical reagents and patients' samples in a centrifugal chemistry analyzer. The cuvette assembly of the present invention advantageously reduces the possibility of undesirable deviations in clinical assay values which may result from this premature mixing.